1. Field of the Invention
The present invention relates generally to integrated circuits, and more particularly but not exclusively to antifuse cells.
2. Description of the Background Art
Some integrated circuits may be configured in the field or the factory after fabrication. Examples of these integrated circuits include programmable logic devices (PLD), field programmable gate arrays (FPGA), read only memories (ROM), and clock circuits. An integrated circuit may be configured by “programming” (also referred to as “burning”) information into it. Programming may involve blowing a fuse that connects two nodes of a circuit. The status of the fuse, i.e., whether it is open or shorted, may be determined by flowing read current through the nodes. An antifuse configures an integrated circuit in a manner opposite to that of a fuse. An antifuse provides an open circuit in a normal state, and provides a short when burned. The state of an antifuse may be read in a manner similar to that of a fuse.
Generally speaking, it is advantageous to have an antifuse that occupies a relatively small area and that has relatively tight read current distribution.